Oil pump device

ABSTRACT

An oil pump device includes an oil circulation flow channel; a gear pump section including a drive gear unit and a driven gear unit; a first branching flow channel that branches from the oil circulation flow channel and communicates with the gear pump section; a hydraulic control valve that drives the driven gear unit; a second branching flow channel that branches from the oil circulation flow channel and communicates with a second small-diameter passage section; a solenoid valve that includes a drain discharge port; an orifice that is disposed between the second small-diameter passage section and the solenoid valve; and a spring that elastically urges the driven gear unit. The solenoid valve performs control in such a manner that the second branching flow channel and the second small-diameter passage section are put to a communicating state or a non-communicating state, and that the drain discharge port communicates with the second small-diameter passage section in the non-communicating state.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an oil pump device that is provided in a variable-capacity pump and can minimize a load imposed on a pump, an engine and the like by changing an oil pressure and a discharge volume to values desirable for the engine and hydraulic equipment.

2. Description of the Related Art

In an external gear pump, the theoretical discharge volume is ordinarily determined by the tooth length and tooth width, and the discharge volume per unit time is determined by the theoretical discharge volume and the rotational speed of the gears (pump revolutions). In a case where such a gear pump is used, for instance, as an oil pump for supplying lubricating oil into an engine for a vehicle, the theoretical discharge volume of the oil pump is set in such a manner that the amount of oil necessary for lubrication can be supplied even when the output of the engine serving as a driving source is low and pump revolutions are low.

When pump revolutions increase accompanying higher engine output, on the other hand, an excessive amount and oil pressure of oil, beyond the required amount, may in some instances be supplied to the engine, and the oil pump may consume thus substantial driving force, which may result engine output loss. Known gear pumps that solve the above problem include variable-capacity gear pumps in which at least one of a drive gear and a driven gear moves in the axial direction as pump revolutions increase, so that a meshing area in the axial direction decreases as a result, and the theoretical discharge volume is reduced accordingly.

SUMMARY OF THE INVENTION

Conventional external gear pumps change the discharge volume inefficiently. Specifically, the discharge volume required and the oil pressure required for the engine or the hydraulic equipment, cannot be achieved for each revolution range. Thus, in a certain revolution range, the discharge volume and the oil pressure might be higher than necessary. Some of the conventional gear pumps even fail to properly respond to the change in the revolutions.

Thus, in order to solve the above problems, the technique disclosed in Japanese Patent Application Laid-open No. 2012-215169 has been developed, and has solved many problems in the conventional technique. However, the technique disclosed in Japanese Patent Application Laid-open No. 2012-215169 fails to cover the function of discharging the oil through a relief operation in an oil circulation flow channel. When a relief valve is additionally provided to achieve the function, the cost and the size increase. Thus, an object of the present invention (technical problem to be solved by the invention) is to implement the relief function with part of a device forming the variable-capacity pumps.

The inventors have made vigorous studies to solve the problem, and thus solved the problem with a first embodiment of the present invention that is an oil pump device including: an oil circulation flow channel; a gear pump section including: a drive gear unit that does not move in an axial direction; a driven gear unit that moves back and forth in the axial direction; and a second small-diameter passage section in which a second small-diameter shaft section of the driven gear unit slides; a first branching flow channel that branches from the oil circulation flow channel and communicates with the gear pump section; a hydraulic control valve that is disposed on the first branching flow channel and drives the driven gear unit in the axial direction; a second branching flow channel that branches from the oil circulation flow channel and communicates with the second small-diameter passage section; a solenoid valve that is disposed on the second branching flow channel and includes a drain discharge port; an orifice that is disposed between the second small-diameter passage section and the solenoid valve; and a spring that is disposed in the second small-diameter passage section and elastically urges the driven gear unit in a direction in which meshing area is increased. The solenoid valve performs control in such a manner that the second branching flow channel and the second small-diameter passage section are put to a communicating state or a non-communicating state, and that the drain discharge port communicates with the second small-diameter passage section in the non-communicating state.

The problem is solved by a second embodiment of the present invention that is the oil pump device in the first embodiment, in which the orifice is provided from the inside to the outside of the second small-diameter passage section. The problem is solved by a third embodiment of the present invention that is the oil pump device in the first or the second embodiment, in which the hydraulic control valve is controlled in such a manner that the first branching flow channel is put to a communicating state or a non-communicating state in accordance with a movement of a spool in the hydraulic control valve.

The problem is solved by a fourth embodiment of the present invention that is the oil pump device in the third embodiment, in which the hydraulic control valve is provided with a relief discharge port, the second small-diameter passage section communicates with the relief discharge port through a relief flow channel, and the hydraulic control valve performs control in such a manner that the relief flow channel is shut off when the first branching flow channel is in the non-communicating state, and the relief flow channel and the relief discharge port are open when the first branching flow channel is in the communicating state. The problem is solved by a fifth embodiment of the present invention that is the oil pump device in the first or the second embodiment, in which the second small-diameter passage section communicates with a drain flow channel through the solenoid valve in a low revolution range and a medium revolution range of an engine, and the second branching flow channel communicates with the orifice through the solenoid valve in a high revolution range of the engine.

In the present invention, the second branching flow channel branching from the oil circulation flow channel for supplying oil for lubricating the engine communicates with the second small-diameter passage section of the gear pump section. Thus, the oil can be sent to the second small-diameter passage section through the second branching flow channel. The solenoid valve disposed on the second branching flow channel is controlled so that the oil passes through or is blocked in the second branching flow channel.

The orifice is provided in the second small-diameter passage section. With the orifice, the pressure from oil flowed into the second small-diameter passage section by direction control performed by the solenoid valve is slightly reduced. Thus, the oil pressure can be kept at an appropriate level. Furthermore, the oil is discharged from the orifice by a small amount at a time. Thus, the orifice also provides a relief function. The relief function is achieved by the solenoid valve and a housing of the gear pump section, and a new relief valve does not need to be provided separately. All things considered, a small size and a low cost of the device as a whole can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing a configuration and an oil circulation flow channel of an engine in a first embodiment of the present invention;

FIG. 2A is a schematic cross-sectional view showing a drive gear and a driven gear in a gear pump section with a maximum meshing area in an axial direction, FIG. 2B is a cross-sectional view taken along a direction of the arrows X1-X1 in FIG. 2A, FIG. 2C is a schematic cross-sectional view showing the drive gear and the driven gear in the gear pump section with a minimum meshing area in the axial direction, and FIG. 2D is a cross-sectional view taken along a direction of the arrows X2-X2 in FIG. 2C;

FIG. 3 is an overall configuration diagram showing operations in a low revolution range of the engine in the present invention;

FIG. 4 is an overall configuration diagram showing operations in a medium revolution range of the engine in the present invention;

FIG. 5 is an overall configuration diagram showing operations in a high revolution range of the engine in the present invention;

FIG. 6 is a diagram showing a main configuration in a second embodiment of the present invention; and

FIG. 7 is a graph showing a relationship between an engine revolution and an oil pressure to describe a process of transitioning from a low revolution range to the high revolution range in the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention are described below with reference to the accompanying drawings. The configuration in the present invention includes mainly an oil circulation flow channel S, a housing A, a gear pump section B, a hydraulic control valve C, a solenoid valve D, and an orifice 36 as shown FIGS. 1 to 3. The main components such as the gear pump section B, the hydraulic control valve C, and the solenoid valve D are incorporated in the housing A.

As an alternative configuration, the gear pump section B, the hydraulic control valve C, and the solenoid valve D may each independently be provided with the housing A. The housings A may be integrated as blocks connected to each other or may be dispersed to appropriate portions in the oil circulation flow channel S.

The gear pump section B includes a pump chamber 2, a driven gear unit 4, and a drive gear unit 5 that are formed in the housing A. The pump chamber 2 includes a driven gear unit chamber 2 a and a drive gear unit chamber 2 b. The driven gear unit chamber 2 a includes a first small-diameter passage section 21, a large-diameter passage section 22, a stepped surface portion 23, and a second small-diameter passage section 24 that are linearly arranged (see FIG. 1). The stepped surface portion 23 is formed as a flat surface orthogonal to an axial direction of the first small-diameter passage section 21.

The drive gear unit chamber 2 b is formed adjacent to the driven gear unit chamber 2 a. The drive gear unit chamber 2 b includes a drive gear receiving section 25, and a shaft hole 26 formed on both upper and lower sides of the drive gear receiving section 25.

Here, in order to better understand the present invention, the up-and-down direction of the housing A is set for convenience, but this does not the actual on-vehicle direction. The passage direction of the driven gear unit chamber 2 a is defined as the up-and-down direction of the housing A. More specifically, the large-diameter passage section 22 is set to be positioned above the first small-diameter passage section 21 such that the large-diameter passage section 22 is positioned on the upper side and the first small-diameter passage section 21 is positioned on the lower side (see FIG. 1 and FIGS. 2A and 2C). The up-and-down direction is similarly applied to the gear pump section B, the hydraulic control valve C, and the solenoid valve D.

The driven gear unit 4 includes a valve piston 4 a, a driven gear 44, and a partition piston 45 (see FIGS. 2A and 2C). The valve piston 4 a is formed by integrating a first small-diameter shaft section 41, a large-diameter section 42, and a second small-diameter shaft section 43 with each other in the axial direction. The first and the second small-diameter sections 41 and 43 have a cylindrical shape. The large-diameter section 42 has a substantially semi-circular or concave circular arc-shaped recess 42 b formed at part of the outer peripheral side face.

The recess 42 b is a portion where the outer peripheral portion of a drive gear 52 enters when the driven gear 44 moves in the axial direction with respect to the drive gear 52 (see FIGS. 2C and 2D). Such a configuration serves to prevent the drive gear 52 and the valve piston 4 a from interfering with each other.

The valve piston 4 a is used in a state where the axial direction thereof runs vertically, with the first small-diameter shaft section 41 on the lower side and the second small-diameter shaft section 43 on the upper side. The lower end of the first small-diameter shaft section 41 is a shaft end surface 41 a. A stepped section formed at the boundary between the first small-diameter shaft section 41 and the large-diameter section 42 is a pressure-receiving surface 42 a. The bottom face of the second small-diameter shaft section 43 (stepped section) is used as a return pressure-receiving surface 43 a (see FIGS. 2A and 2C).

The drive gear unit 5 includes a drive shaft 51 and the drive gear 52 (see FIG. 1 and FIGS. 2A and 2C). In the drive gear unit 5, the drive gear 52 is accommodated in the drive gear receiving section 25, and the drive shaft 51 is accommodated in the drive gear unit chamber 2 b while being rotatably supported in the shaft hole 26. The drive shaft 51 is rotated by the motive power from an engine crankshaft, not shown. The drive gear 52, which rotates together with the drive shaft 51, transmits the rotation of the drive shaft 51 to the driven gear 44 and works as an external gear pump.

A spring 81 that elastically urges the driven gear unit 4 constantly in a discharge increase direction is fitted in the second small-diameter passage section 24 (see FIG. 1 and FIGS. 2A and 2C). A coil spring is used as the spring 81. The spring 81 exerts elastic urging so as to maximize the meshing area between the driven gear 44 and the drive gear 52.

A first branching flow channel 31 is provided at a position on the upstream side of the engine in the oil circulation flow channel S. The first branching flow channel 31 is formed to communicate with the lower side of the large-diameter passage section 22 in the driven gear unit chamber 2 a. In the oil circulation flow channel S, oil that flows toward the engine partially flows to the first branching flow channel 31 to be sent to the large-diameter passage section 22.

The oil flowing in the large large-diameter passage section 22 is controlled by the hydraulic control valve C described later, so that the pressure-receiving surface 42 a of the valve piston 4 a receives the pressure from the oil. Pressure from the oil is hereinafter also referred to as oil pressure. The first branching flow channel 31 communicates with the large-diameter passage section 22 of the driven gear unit chamber 2 a. The hydraulic control valve C is provided at an intermediate portion of the first branching flow channel 31. In the first branching flow channel 31, the flow channel between the hydraulic control valve C and the large-diameter passage section 22 is referred to as a first branch connection flow channel 311. The first branch connection flow channel 311 is part of the first branching flow channel 31. The hydraulic control valve C passes through or blocks the oil flowing in the first branch connection flow channel 311.

The hydraulic control valve C includes a spool 61, a spool chamber 62 containing the spool 61, and a spring 82. The spool 61 includes two large-diameter sections 61 a and 61 b and a small-diameter section 61 c. The small-diameter section 61 c is linearly arranged between the two large-diameter sections 61 a and 61 b. A portion of the spool 61 around the small-diameter section 61 c is a recess section 61 d. In the spool chamber 62, a first flow port 62 a, a second flow port 62 b, a relief switching aperture 62 c, and a relief discharge port 62 d are formed. With the elastic urging force of the spring 82, the first flow port 62 a and the second flow port 62 b are constantly closed by the large-diameter section 61 a of the spool 61, and the relief switching aperture 62 c and the relief discharge port 62 d are constantly closed by the large-diameter section 61 b.

The hydraulic control valve C performs switching control of communication and shut-off between the first branching flow channel 31 and the large-diameter passage section 22. More specifically, the oil in the first branching flow channel 31 flows in through the first flow port 62 a and the oil pressure is applied to an end surface of the large-diameter section 61 a of the spool 61. When an oil pressure of a predetermined level or higher is applied, the spool 61 moves upward. Thus, the large-diameter section 61 a that has been closing the second flow port 62 b moves upward and thus the second flow port 62 b opens. As a result, the oil flows into the first branch connection flow channel 311 and then into the large-diameter passage section 22 to push up the pressure-receiving surface 42 a of the driven gear unit 4.

Next, the solenoid valve D will be described. The solenoid valve D includes a direction control valve 71, a solenoid section 72, and a direction control valve chamber 73. An inner valve control flow channel 71 a is formed in the direction control valve 71. A direction control flow inlet 73 a, a direction control flow outlet 73 b, and a drain discharge port 73 c are formed in the direction control valve chamber 73.

The direction control valve 71 is controlled by the solenoid section 72, so that the inner valve control flow channel 71 a of the direction control valve 71 selects the direction control flow outlet 73 b or the drain discharge port 73 c to communicate with the direction control flow inlet 73 a. When the selected one is put to a communicating state, the other one is put to a shut-off state, that is, a non-communicating state.

The second branching flow channel 33 communicates with the second small-diameter passage section 24 of the pump chamber 2. In the second branching flow channel 33, a flow channel between the solenoid valve 7 and the second small-diameter passage section 24 is referred to as a second connection flow channel 331. The second connection flow channel 331 is part of the second branching flow channel 33. The drain discharge port 73 c includes a drain flow channel 35 through which the oil is discharged to the outside from the oil circulation flow channel S or sent to an oil pan.

In the second branching flow channel 33, the orifice 36 is provided in the second connection flow channel 331. With the orifice 36, the oil flows into or is discharged from the second small-diameter passage section 24 by a small amount at a time.

A relief inlet 24 a is positioned above the second small-diameter passage section 24 of the driven gear unit chamber 2 a. The relief inlet 24 a communicates with the second connection flow channel 331 of the second branching flow channel 33. A relief outlet 24 b is formed at the same position as, or below, the relief inlet 24 a.

Thus, with the orifice 36, when the second small-diameter passage section 24 is filled with oil with a pressure, the oil can be discharged from the second small-diameter passage section 24 by a small amount at a time while the pressure is kept at a substantially constant level.

The orifice 36 and the relief inlet 24 a may be formed as separate members or may be integrally formed. In a case where the orifice 36 and the relief inlet 24 a are integrally formed, the relief inlet 24 a may be formed as a small-diameter pipe or a pipe in which a throttle section is formed as a small internal diameter section, to be able to function as the orifice 36.

The relief outlet 24 b of the second small-diameter passage section 24 communicates with the relief switching aperture 62 c of the hydraulic control valve C via the relief flow channel 37. When the large-diameter section 61 b moves upward along with the movement of the spool 61 of the hydraulic control valve C, the relief switching aperture 62 c communicates with the relief discharge port 62 d in the spool chamber 62 through the recess section 61 d formed by the small-diameter section 61 c. Thus, the relief outlet 24 b communicates with the relief discharge port 62 d, whereby the oil can be discharged from the second small-diameter passage section 24.

Next, a direction control action of the hydraulic control valve C will be described. The oil pump device of the present invention is incorporated in the oil circulation flow channel S of the engine 100. The oil flows into the first branching flow channel 31 of the housing A from the oil circulation flow channel S.

The oil flowing into the first branching flow channel 31 causes the spool 61 of the hydraulic control valve C to operate so as to put the first flow port 62 a and the large-diameter passage section 22 to the communicating state or the non-communicating (shut-off) state. In the communicating state, the oil pressure is applied to the pressure-receiving surface 42 a of the driven gear unit 4, whereby the driven gear unit 4 moves upward in the radial direction. As a result, the meshing area between the driven gear 44 and the drive gear 52 becomes small, and the oil discharge volume is reduced (see FIG. 4).

Next, a direction control action of the solenoid valve D will be described. When the solenoid valve D is ON, the solenoid section 72 controls the direction control valve 71 in such a manner that the second branching flow channel 33 does not communicate with the relief inlet 24 a of the second small-diameter passage section 24. Thus, the oil flowing into the second branching flow channel 33 from the oil circulation flow channel S cannot flow into the second small-diameter passage section 24 (see FIGS. 3 and 4). On the other hand, the drain discharge port 73 c communicates with the relief inlet 24 a of the second small-diameter passage section 24, whereby the oil in the second small-diameter passage section 24 is discharged through the drain discharge port 73 c.

When the solenoid valve D is OFF, the solenoid section 72 switches the inner valve control flow channel 71 a of the direction control valve 71. Thus, the second branching flow channel 33 communicates with the second small-diameter passage section 24 of the gear pump section B, whereby the oil flows into the second small-diameter passage section 24. As a result, the oil pressure and the urging force from the spring 81 are applied to the return pressure-receiving surface 43 a of the driven gear unit 4.

When the force applied by the oil pressure and the urging force from the spring 81 to the return pressure-receiving surface 43 a on the side of the second small-diameter passage section 24 is greater than the force applied by the pressure-receiving surface 42 a on the side of the first branching flow channel 31, the driven gear unit 4 stays on the side of the first small-diameter passage section 21. Thus, the discharge volume is at a normal level with the maximum meshing area between the drive gear 52 and the driven gear 44.

The operation of the present invention will be explained next for various revolution ranges of the engine 100. The oil pump device of the present invention sets an appropriate discharge volume in the gear pump section B in accordance with the revolutions Ne of the engine 100. The discharge volume varies among a low revolution range, medium revolution range, and high revolution range of the revolutions Ne.

An operation will be explained first for the low revolution range of the engine revolutions Ne (see FIG. 3). In the low revolution range, the revolutions Ne take on a value from that in the idling state to about 1000 rpm. The solenoid valve D is ON, and thus the direction control valve 71 shuts off the communication between the second branching flow channel 33 and the second small-diameter passage section 24, so that the non-communication state is achieved. The second small-diameter passage section 24 is in communication with the drain discharge port 73 c through the inner valve control flow channel 71 a of the direction control valve 71, and thus is in communication with and opened to the atmosphere. All things considered, only the force from the spring 81 is applied to the driven gear unit 4 through the return pressure-receiving surface 43 a of the second small-diameter passage section 24.

The hydraulic control valve C performs control so that the pressure from the oil flowing in the first branching flow channel 31 is applied or not applied to the pressure-receiving surface 42 a of the driven gear unit 4. The oil pressure generated by the external gear pump to be applied to the spool 61 of the hydraulic control valve C is small in the low revolution range. Thus, the urging force of the spring 81 is greater than the force applied by the oil pressure, whereby the driven gear unit 4 does not move. Accordingly, the driven gear 44 meshes with the drive gear 52 entirely in the axial direction, whereby the discharge volume of the pump per revolution is at the maximum level. In the low revolution range, the oil pressure is substantially proportional to the engine revolutions.

An operation will be explained next for the medium revolution range of the engine 100 (see FIG. 4). In the medium revolution range, the revolutions Ne take on a value from about 1000 rpm to about 3500 rpm. The force applied to the spool 61 of the hydraulic control valve C by the oil pressure is greater than the elastic urging force of the spring 82 when the engine revolutions reach a predetermined value Net (about 1000 rpm). Thus, the spool 61 moves upward in the axial direction so that the first flow port 62 a communicates with the second flow port 62 b in the spool chamber 62, whereby the first branching flow channel 31 communicates with the large-diameter passage section 22. As a result, the force of the oil pressure is applied to the pressure-receiving surface 42 a.

In the medium revolution range, the solenoid valve D is ON, and thus the direction control valve 71 shuts off the communication between the second branching flow channel 33 and the second small-diameter passage section 24 so that the non-communication state is achieved, as in the case of the low revolution range. The second small-diameter passage section 24 is in communication with the drain discharge port 73 c through the inner valve control flow channel 71 a of the direction control valve 71.

Thus, the second small-diameter passage section 24 is in communication with and opened to the atmosphere, whereby in the second small-diameter passage section 24, only the force from the spring 81 is applied to the return pressure-receiving surface 43 a of the driven gear unit 4. The force applied to the pressure-receiving surface 42 a of the valve piston 4 a is greater than the force applied to the return pressure-receiving surface 43 a. As a result, the driven gear unit 4 moves to the side of the second small-diameter passage section 24.

Thus, the meshing area between the drive gear 52 and the driven gear 44 becomes narrower, and the theoretical discharge volume decreases gradually. All things considered, in the medium revolution range, the oil pressure is kept at a substantially constant low level over a wide range of revolutions. Thus, the load on the pump itself and the power loss of the engine can be reduced, whereby the fuel efficiency can be improved.

A relief operation in the high revolution range of revolutions Ne in the engine 100 will be explained next (see FIG. 5). Specifically, the revolutions Ne in the high revolution range are about 3500 rpm or more. The discharge volume of the gear pump section B is large in the high revolution range. The solenoid valve D is OFF, and thus, with the direction control valve 71 switched by the solenoid section 72, the second branching flow channel 33 communicates with the second small-diameter passage section 24 through the inner valve control flow channel 71 a.

Thus, the oil flows into the second small-diameter passage section 24 from the second branching flow channel 33, to apply the oil pressure to the return pressure-receiving surface 43 a of the driven gear unit 4. As a result, the driven gear unit 4 moves in a direction in which the area of meshing with the drive gear 52 increases, whereby the discharge volume and discharge pressure of the pump increase.

The discharge pressure of the pump thus increased moves the spool 61 upward, whereby the hydraulic control valve C and the relief flow channel 37 make the second small-diameter passage section 24 communicate with the relief switching aperture 62 c. The spool 61 moves the spool chamber 62 upward by the oil pressure from the first branching flow channel 31. Thus, the large diameter portion 61 b of the spool 61 opens the relief switching aperture 62 c and the relief discharge port 62 d. The relief switching aperture 62 c communicates with the relief discharge port 62 d through the recess section 61 d.

Then, the relief operation is performed. Specifically, the oil in the second small-diameter passage section 24 returns to the oil pan disposed outside the oil circulation flow channel S through a return flow channel 38 connected to the relief flow channel 37 and the relief discharge port 62 d of the hydraulic control valve C. Thus, the oil pressure only slightly rises along with the increase of the engine revolutions (see FIG. 7).

The oil pressure in the second small-diameter passage section 24 is further reduced by the orifice 36 provided in the second connection flow channel 331. Thus, the force applied to the pressure-receiving surface 42 a by the oil pressure is greater than the force applied by the spring 81 and by the pressure from the oil in the second small-diameter passage section 24. As a result, the driven gear unit 4 moves in a direction in which the area of meshing with the drive gear unit 5 is reduced. All things considered, the oil pressure can be kept constant even when the revolutions increase.

FIG. 6 shows a second embodiment of the present invention, in which the second small-diameter passage section 24 is not provided with the relief outlet 24 b. The relief operation is performed with the drain discharge port 73 c through the solenoid valve D.

In the second embodiment, the orifice is provided from the inside to the outside of the second small-diameter passage section. Thus, the oil in the second small-diameter passage section can be directly discharged to the outside through the orifice, to be received by the oil pan and the like. All things considered, an extremely simple relief device can be achieved.

In a third embodiment, the hydraulic control valve puts the first branching flow channel in the communicating or non-communicating state in accordance with the movement of the spool inside the hydraulic control valve. Thus, the movement of the driven gear in the axial direction can be controlled in accordance with the increase/decrease of the pressure from the oil in the oil circulation flow channel. Furthermore, the hydraulic control valve is almost completely free of troubles due to a failure in the electrical system, which happens when an electric control valve is used, and thus ensures stable use.

In a fourth embodiment, the hydraulic control valve is provided with a relief discharge port. The second small-diameter passage section communicates with the relief discharge port through the relief flow channel. The hydraulic control valve has the following configuration. Specifically, the relief flow channel is shut-off when the first branching flow channel is in the non-communicating state, and the relief flow channel and the relief discharge port are open when the first branching flow channel is in the communicating state. Thus, the movement of the driven gear in the axial direction can be controlled in accordance with the change in the pressure from the oil in the oil circulation flow channel.

In a stage where the oil pressure is low in the low revolution range of the engine, the relief flow channel is closed when the first branching flow channel is in the non-communicating state. Thus, the oil in the second small-diameter passage section is less likely to be discharged. Accordingly, the movement of the driven gear unit in the direction in which the area of meshing with the drive gear unit is reduced can be surely prevented. As a result, the oil can be circulated even more stably in the low revolution range.

The relief flow channel and the relief discharge port are open when the first branching flow channel is in the communicating state. Thus, for example, in the high revolution range of the engine, the oil in the second small-diameter passage section can be discharged to the outside through the relief flow channel and the relief discharge port of the hydraulic control valve. Thus, the driven gear suitably moves in accordance with the change in the oil pressure due to the change in the revolutions, whereby the appropriate oil discharge volume can be set. The oil is relieved (discharged) from the hydraulic control valve. Thus, the hydraulic control valve also serves as a relief valve, and thus a relief valve does not need to be provided separately.

In a fifth embodiment, the second small-diameter passage section communicates with the drain flow channel through the solenoid valve in the low and medium revolution ranges of the engine, and the second branching flow channel communicates with the orifice through the solenoid valve in the high revolution range of the engine. Thus, the optimum discharge volume can be set for each revolution range. 

1. An oil pump device comprising: an oil circulation flow channel; a gear pump section including: a drive gear unit that does not move in an axial direction; a driven gear unit that moves back and forth in the axial direction; and a second small-diameter passage section in which a second small-diameter shaft section of the driven gear unit slides; a first branching flow channel that branches from the oil circulation flow channel and communicates with the gear pump section; a hydraulic control valve that is disposed on the first branching flow channel and drives the driven gear unit in the axial direction; a second branching flow channel that branches from the oil circulation flow channel and communicates with the second small-diameter passage section; a solenoid valve that is disposed on the second branching flow channel and includes a drain discharge port; an orifice that is disposed between the second small-diameter passage section and the solenoid valve; and a spring that is disposed in the second small-diameter passage section and elastically urges the driven gear unit in a direction in which meshing area is increased, wherein the solenoid valve performs control in such a manner that the second branching flow channel and the second small-diameter passage section are put to a communicating state or a non-communicating state, and that the drain discharge port communicates with the second small-diameter passage section in the non-communicating state.
 2. The oil pump device according to claim 1, wherein the orifice is provided from the inside to the outside of the second small-diameter passage section.
 3. The oil pump device according to claim 1, wherein the hydraulic control valve is controlled in such a manner that the first branching flow channel is put to a communicating state or a non-communicating state in accordance with a movement of a spool in the hydraulic control valve.
 4. The oil pump device according to claim 3, wherein the hydraulic control valve is provided with a relief discharge port, the second small-diameter passage section communicates with the relief discharge port through a relief flow channel, and the hydraulic control valve performs control in such a manner that the relief flow channel is shut off when the first branching flow channel is in the non-communicating state, and the relief flow channel and the relief discharge port are open when the first branching flow channel is in the communicating state.
 5. The oil pump device according to claim 1, wherein the second small-diameter passage section communicates with a drain flow channel through the solenoid valve in a low revolution range and a medium revolution range of an engine, and the second branching flow channel communicates with the orifice through the solenoid valve in a high revolution range of the engine. 